As a hotspot for researches and application developments in the field of computer vision, a depth perception technology is intended for perceiving shape and distance information of a spatial object. Compared with a binocular stereoscopic camera, a structured light-based active vision depth perception technology may acquire depth information of an image more accurately, and the depth image information acquired thereby has the following advantages: a higher stability and reliability, insusceptibility to ambient light, a simple stereoscopic matching process, and a low algorithm computation complexity, etc. Specifically, a laser speckle projector is one of key devices applying the structured light depth perception technology, and the coded pattern projected thereby will directly affect the complexity of depth decoding computation as well as the precision and resolution of depth measurement.
Compared with a light-emitting diode LED and a laser diode LD, a Vertical Cavity Surface Emitting Laser (VCSEL) has an optical cavity oriented perpendicular to a semiconductor wafer such that it may emit light from a surface; the VCSEL has advantages such as a smaller size, a circular output light spot, a single longitudinal mode output, a lower threshold current, a lower price, and ease to be integrated into a large-area array, etc.; therefore, it has been widely applied in fields of optical communication, optical interconnects, and optical storage, etc.
Structurally, the laser speckle projector mainly comprises a light source, a collimator and/or a Diffractive Optical Element (DOE), wherein most laser speckle projectors exploit a single point light source to emit light vertically or to emit light laterally in combination with a 45° (45 degree) reflection, and thus has problems such as a large size, a low photoelectric conversion efficiency, and a large temperature drift effect, etc.; some laser speckle projectors adopt an irregular random VCSEL lattice arrangement to project a basic coded pattern; the basic coded pattern is projected after being duplicated by the diffractive optical element DOE; its lattice arrangement is a random light-emitting lattice and thus has problems that the precision of lattice arrangement position is not high enough, the lattice production density is limited, and the product yield is low; moreover, when the random light-emitting lattice as a basic coded pattern is duplicated and spliced through the DOE, the edge lattices of the pattern easily overlap or are too sparse, causing that the finally formed laser speckle coded pattern is largely discrepant from the designed coded pattern. Besides, the speckle coded patterns projected by existing laser speckle projectors are substantially fixed and invariable; when they are used for space coding a target object or a projection space, they are largely susceptible to ambient light during a structured light depth perception process, which is disadvantageous to improve the accuracy and robustness of depth measurement.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.